Actions of neurotransmitters have so far been shown to take place at two principal sites: (1) ion gating channels, (2) control of ion pumps. The action of acetylcholine (Ach) belongs to the first type where it appears that the gating process is due to interaction between an ion channel and a receptor. The latter may vary from tissue to tissue conferring different ion selectivities on the channel. It is proposed to dissect Ach receptor from different tissues using proteolytic enzymes and characterize the components with respect to (1) ion channel activity in a lipid bilayer, (2) agonist binding. The second mode of action involves a complicated sequence of events terminating in the modulation of an ion pump. It is proposed to study the role of the lipid environment for the ATP driven H-K ions exchange pump from gastric mucosa. It is believed that this pump is a prototype for others (e.g., sarcoplasmic reticulum Ca ions, kidney tubule Na-K ions) which are less easy to work with. BIBLIOGRAPHIC REFERENCE: Sachs, G., Saccomani, G., Lewin, M., Hung, P., Schackmann, R., Rabon, E., Goodall, M.C.: Transport properties of a membrane fraction of gastric mucosa. Vth Intl. Biophys. Congress, 1975.